<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    .box {
      width: 300px;
      height: 300px;
      background-color: #f00;

      /* 防止margin-top传递 */
      /* 方法一 */
      /* border: 1px solid rgba(0, 0, 0, 0); */
      /* 方法二 */
      overflow: auto;
    }

    .container {
      width: 100px;
      height: 100px;
      background-color: #0f0;
      /* 左右不会传递 */
      /* margin-left: 30px; */

      /* 上下会传递,相当于box向下100px */
      margin-top: 100px;
    }
  </style>
</head>

<body>
  <div class="box">
    <div class="container"></div>
  </div>
</body>

</html>